/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef jit_JitcodeMap_h
#define jit_JitcodeMap_h

#include "jit/CompactBuffer.h"
#include "jit/CompileInfo.h"
#include "jit/ExecutableAllocator.h"
#include "jit/OptimizationTracking.h"
#include "jit/shared/CodeGenerator-shared.h"

namespace js {
namespace jit {

/*
 * The Ion jitcode map implements tables to allow mapping from addresses in ion jitcode
 * to the list of (JSScript*, jsbytecode*) pairs that are implicitly active in the frame at
 * that point in the native code.
 *
 * To represent this information efficiently, a multi-level table is used.
 *
 * At the top level, a global splay-tree of JitcodeGlobalEntry describings the mapping for
 * each individual IonCode script generated by compiles.  The entries are ordered by their
 * nativeStartAddr.
 *
 * Every entry in the table is of fixed size, but there are different entry types,
 * distinguished by the kind field.
 */

class JitcodeGlobalTable;
class JitcodeIonTable;
class JitcodeRegionEntry;

class JitcodeGlobalEntry;

class JitcodeSkiplistTower
{
  public:
    static const unsigned MAX_HEIGHT = 32;

  private:
    uint8_t height_;
    bool isFree_;
    JitcodeGlobalEntry* ptrs_[1];

  public:
    explicit JitcodeSkiplistTower(unsigned height)
      : height_(height),
        isFree_(false)
    {
        MOZ_ASSERT(height >= 1 && height <= MAX_HEIGHT);
        clearPtrs();
    }

    unsigned height() const {
        return height_;
    }

    JitcodeGlobalEntry** ptrs(unsigned level) {
        return ptrs_;
    }

    JitcodeGlobalEntry* next(unsigned level) const {
        MOZ_ASSERT(!isFree_);
        MOZ_ASSERT(level < height());
        return ptrs_[level];
    }
    void setNext(unsigned level, JitcodeGlobalEntry* entry) {
        MOZ_ASSERT(!isFree_);
        MOZ_ASSERT(level < height());
        ptrs_[level] = entry;
    }

    //
    // When stored in a free-list, towers use 'ptrs_[0]' to store a
    // pointer to the next tower.  In this context only, 'ptrs_[0]'
    // may refer to a |JitcodeSkiplistTower*| instead of a
    // |JitcodeGlobalEntry*|.
    //

    void addToFreeList(JitcodeSkiplistTower** freeList) {
        JitcodeSkiplistTower* nextFreeTower = *freeList;
        MOZ_ASSERT_IF(nextFreeTower, nextFreeTower->isFree_ &&
                                     nextFreeTower->height() == height_);
        ptrs_[0] = (JitcodeGlobalEntry*) nextFreeTower;
        isFree_ = true;
        *freeList = this;
    }

    static JitcodeSkiplistTower* PopFromFreeList(JitcodeSkiplistTower** freeList) {
        if (!*freeList)
            return nullptr;

        JitcodeSkiplistTower* tower = *freeList;
        MOZ_ASSERT(tower->isFree_);
        JitcodeSkiplistTower* nextFreeTower = (JitcodeSkiplistTower*) tower->ptrs_[0];
        tower->clearPtrs();
        tower->isFree_ = false;
        *freeList = nextFreeTower;
        return tower;
    }

    static size_t CalculateSize(unsigned height) {
        MOZ_ASSERT(height >= 1);
        return sizeof(JitcodeSkiplistTower) +
               (sizeof(JitcodeGlobalEntry*) * (height - 1));
    }

  private:
    void clearPtrs() {
        for (unsigned i = 0; i < height_; i++)
            ptrs_[0] = nullptr;
    }
};

class JitcodeGlobalEntry
{
    friend class JitcodeGlobalTable;

  public:
    enum Kind {
        INVALID = 0,
        Ion,
        Baseline,
        IonCache,
        Dummy,
        Query,
        LIMIT
    };
    JS_STATIC_ASSERT(LIMIT <= 8);

    struct BytecodeLocation {
        JSScript* script;
        jsbytecode* pc;
        BytecodeLocation(JSScript* script, jsbytecode* pc) : script(script), pc(pc) {}
    };
    typedef Vector<BytecodeLocation, 0, SystemAllocPolicy> BytecodeLocationVector;
    typedef Vector<const char*, 0, SystemAllocPolicy> ProfileStringVector;

    struct BaseEntry
    {
        JitCode* jitcode_;
        void* nativeStartAddr_;
        void* nativeEndAddr_;
        uint32_t gen_;
        Kind kind_ : 7;

        void init() {
            jitcode_ = nullptr;
            nativeStartAddr_ = nullptr;
            nativeEndAddr_ = nullptr;
            gen_ = UINT32_MAX;
            kind_ = INVALID;
        }

        void init(Kind kind, JitCode* code,
                  void* nativeStartAddr, void* nativeEndAddr)
        {
            MOZ_ASSERT_IF(kind != Query, code);
            MOZ_ASSERT(nativeStartAddr);
            MOZ_ASSERT(nativeEndAddr);
            MOZ_ASSERT(kind > INVALID && kind < LIMIT);
            jitcode_ = code;
            nativeStartAddr_ = nativeStartAddr;
            nativeEndAddr_ = nativeEndAddr;
            gen_ = UINT32_MAX;
            kind_ = kind;
        }

        uint32_t generation() const {
            return gen_;
        }
        void setGeneration(uint32_t gen) {
            gen_ = gen;
        }
        bool isSampled(uint32_t currentGen, uint32_t lapCount) {
            if (gen_ == UINT32_MAX || currentGen == UINT32_MAX)
                return false;
            MOZ_ASSERT(currentGen >= gen_);
            return (currentGen - gen_) <= lapCount;
        }

        Kind kind() const {
            return kind_;
        }
        JitCode* jitcode() const {
            return jitcode_;
        }
        void* nativeStartAddr() const {
            return nativeStartAddr_;
        }
        void* nativeEndAddr() const {
            return nativeEndAddr_;
        }

        bool startsBelowPointer(void* ptr) const {
            return ((uint8_t*)nativeStartAddr()) <= ((uint8_t*) ptr);
        }
        bool endsAbovePointer(void* ptr) const {
            return ((uint8_t*)nativeEndAddr()) > ((uint8_t*) ptr);
        }
        bool containsPointer(void* ptr) const {
            return startsBelowPointer(ptr) && endsAbovePointer(ptr);
        }

        template <class ShouldMarkProvider> bool markJitcode(JSTracer* trc);
        bool isJitcodeMarkedFromAnyThread(JSRuntime* rt);
        bool isJitcodeAboutToBeFinalized();
    };

    struct IonEntry : public BaseEntry
    {
        // regionTable_ points to the start of the region table within the
        // packed map for compile represented by this entry.  Since the
        // region table occurs at the tail of the memory region, this pointer
        // points somewhere inside the region memory space, and not to the start
        // of the memory space.
        JitcodeIonTable* regionTable_;

        // optsRegionTable_ points to the table within the compact
        // optimizations map indexing all regions that have tracked
        // optimization attempts. optsTypesTable_ is the tracked typed info
        // associated with the attempts vectors; it is the same length as the
        // attempts table. optsAttemptsTable_ is the table indexing those
        // attempts vectors.
        //
        // All pointers point into the same block of memory; the beginning of
        // the block is optRegionTable_->payloadStart().
        const IonTrackedOptimizationsRegionTable* optsRegionTable_;
        const IonTrackedOptimizationsTypesTable* optsTypesTable_;
        const IonTrackedOptimizationsAttemptsTable* optsAttemptsTable_;

        // The types table above records type sets, which have been gathered
        // into one vector here.
        IonTrackedTypeVector* optsAllTypes_;

        struct ScriptNamePair {
            JSScript* script;
            char* str;
        };

        struct SizedScriptList {
            uint32_t size;
            ScriptNamePair pairs[1];
            SizedScriptList(uint32_t sz, JSScript** scrs, char** strs) : size(sz) {
                for (uint32_t i = 0; i < size; i++) {
                    pairs[i].script = scrs[i];
                    pairs[i].str = strs[i];
                }
            }

            static uint32_t AllocSizeFor(uint32_t nscripts) {
                return sizeof(SizedScriptList) + ((nscripts - 1) * sizeof(ScriptNamePair));
            }
        };

        SizedScriptList* scriptList_;

        void init(JitCode* code, void* nativeStartAddr, void* nativeEndAddr,
                  SizedScriptList* scriptList, JitcodeIonTable* regionTable)
        {
            MOZ_ASSERT(scriptList);
            MOZ_ASSERT(regionTable);
            BaseEntry::init(Ion, code, nativeStartAddr, nativeEndAddr);
            regionTable_ = regionTable;
            scriptList_ = scriptList;
            optsRegionTable_ = nullptr;
            optsTypesTable_ = nullptr;
            optsAllTypes_ = nullptr;
            optsAttemptsTable_ = nullptr;
        }

        void initTrackedOptimizations(const IonTrackedOptimizationsRegionTable* regionTable,
                                      const IonTrackedOptimizationsTypesTable* typesTable,
                                      const IonTrackedOptimizationsAttemptsTable* attemptsTable,
                                      IonTrackedTypeVector* allTypes)
        {
            optsRegionTable_ = regionTable;
            optsTypesTable_ = typesTable;
            optsAttemptsTable_ = attemptsTable;
            optsAllTypes_ = allTypes;
        }

        SizedScriptList* sizedScriptList() const {
            return scriptList_;
        }

        unsigned numScripts() const {
            return scriptList_->size;
        }

        JSScript* getScript(unsigned idx) const {
            MOZ_ASSERT(idx < numScripts());
            return sizedScriptList()->pairs[idx].script;
        }

        const char* getStr(unsigned idx) const {
            MOZ_ASSERT(idx < numScripts());
            return sizedScriptList()->pairs[idx].str;
        }

        void destroy();

        JitcodeIonTable* regionTable() const {
            return regionTable_;
        }

        int scriptIndex(JSScript* script) const {
            unsigned count = numScripts();
            for (unsigned i = 0; i < count; i++) {
                if (getScript(i) == script)
                    return i;
            }
            return -1;
        }

        void* canonicalNativeAddrFor(JSRuntime*rt, void* ptr) const;

        MOZ_MUST_USE bool callStackAtAddr(JSRuntime* rt, void* ptr, BytecodeLocationVector& results,
                                          uint32_t* depth) const;

        uint32_t callStackAtAddr(JSRuntime* rt, void* ptr, const char** results,
                                 uint32_t maxResults) const;

        void youngestFrameLocationAtAddr(JSRuntime* rt, void* ptr,
                                         JSScript** script, jsbytecode** pc) const;

        bool hasTrackedOptimizations() const {
            return !!optsRegionTable_;
        }

        const IonTrackedOptimizationsRegionTable* trackedOptimizationsRegionTable() const {
            MOZ_ASSERT(hasTrackedOptimizations());
            return optsRegionTable_;
        }

        uint8_t numOptimizationAttempts() const {
            MOZ_ASSERT(hasTrackedOptimizations());
            return optsAttemptsTable_->numEntries();
        }

        IonTrackedOptimizationsAttempts trackedOptimizationAttempts(uint8_t index) {
            MOZ_ASSERT(hasTrackedOptimizations());
            return optsAttemptsTable_->entry(index);
        }

        IonTrackedOptimizationsTypeInfo trackedOptimizationTypeInfo(uint8_t index) {
            MOZ_ASSERT(hasTrackedOptimizations());
            return optsTypesTable_->entry(index);
        }

        const IonTrackedTypeVector* allTrackedTypes() {
            MOZ_ASSERT(hasTrackedOptimizations());
            return optsAllTypes_;
        }

        mozilla::Maybe<uint8_t> trackedOptimizationIndexAtAddr(
            JSRuntime *rt,
            void* ptr,
            uint32_t* entryOffsetOut);

        void forEachOptimizationAttempt(JSRuntime* rt, uint8_t index,
                                        JS::ForEachTrackedOptimizationAttemptOp& op);
        void forEachOptimizationTypeInfo(JSRuntime* rt, uint8_t index,
                                         IonTrackedOptimizationsTypeInfo::ForEachOpAdapter& op);

        template <class ShouldMarkProvider> bool mark(JSTracer* trc);
        void sweepChildren();
        bool isMarkedFromAnyThread(JSRuntime* rt);
    };

    struct BaselineEntry : public BaseEntry
    {
        JSScript* script_;
        const char* str_;

        // Last location that caused Ion to abort compilation and the reason
        // therein, if any. Only actionable aborts are tracked. Internal
        // errors like OOMs are not.
        jsbytecode* ionAbortPc_;
        const char* ionAbortMessage_;

        void init(JitCode* code, void* nativeStartAddr, void* nativeEndAddr,
                  JSScript* script, const char* str)
        {
            MOZ_ASSERT(script != nullptr);
            BaseEntry::init(Baseline, code, nativeStartAddr, nativeEndAddr);
            script_ = script;
            str_ = str;
        }

        JSScript* script() const {
            return script_;
        }

        const char* str() const {
            return str_;
        }

        void trackIonAbort(jsbytecode* pc, const char* message) {
            MOZ_ASSERT(script_->containsPC(pc));
            MOZ_ASSERT(message);
            ionAbortPc_ = pc;
            ionAbortMessage_ = message;
        }

        bool hadIonAbort() const {
            MOZ_ASSERT(!ionAbortPc_ || ionAbortMessage_);
            return ionAbortPc_ != nullptr;
        }

        void destroy();

        void* canonicalNativeAddrFor(JSRuntime* rt, void* ptr) const;

        MOZ_MUST_USE bool callStackAtAddr(JSRuntime* rt, void* ptr, BytecodeLocationVector& results,
                                          uint32_t* depth) const;

        uint32_t callStackAtAddr(JSRuntime* rt, void* ptr, const char** results,
                                 uint32_t maxResults) const;

        void youngestFrameLocationAtAddr(JSRuntime* rt, void* ptr,
                                         JSScript** script, jsbytecode** pc) const;

        template <class ShouldMarkProvider> bool mark(JSTracer* trc);
        void sweepChildren();
        bool isMarkedFromAnyThread(JSRuntime* rt);
    };

    struct IonCacheEntry : public BaseEntry
    {
        void* rejoinAddr_;
        JS::TrackedOutcome trackedOutcome_;

        void init(JitCode* code, void* nativeStartAddr, void* nativeEndAddr,
                  void* rejoinAddr, JS::TrackedOutcome trackedOutcome)
        {
            MOZ_ASSERT(rejoinAddr != nullptr);
            BaseEntry::init(IonCache, code, nativeStartAddr, nativeEndAddr);
            rejoinAddr_ = rejoinAddr;
            trackedOutcome_ = trackedOutcome;
        }

        void* rejoinAddr() const {
            return rejoinAddr_;
        }
        JS::TrackedOutcome trackedOutcome() const {
            return trackedOutcome_;
        }

        void destroy() {}

        void* canonicalNativeAddrFor(JSRuntime* rt, void* ptr) const;

        MOZ_MUST_USE bool callStackAtAddr(JSRuntime* rt, void* ptr, BytecodeLocationVector& results,
                                          uint32_t* depth) const;

        uint32_t callStackAtAddr(JSRuntime* rt, void* ptr, const char** results,
                                 uint32_t maxResults) const;

        void youngestFrameLocationAtAddr(JSRuntime* rt, void* ptr,
                                         JSScript** script, jsbytecode** pc) const;

        bool hasTrackedOptimizations() const { return true; }
        mozilla::Maybe<uint8_t> trackedOptimizationIndexAtAddr(
            JSRuntime *rt,
            void* ptr,
            uint32_t* entryOffsetOut);
        void forEachOptimizationAttempt(JSRuntime* rt, uint8_t index,
                                        JS::ForEachTrackedOptimizationAttemptOp& op);
        void forEachOptimizationTypeInfo(JSRuntime* rt, uint8_t index,
                                         IonTrackedOptimizationsTypeInfo::ForEachOpAdapter& op);

        template <class ShouldMarkProvider> bool mark(JSTracer* trc);
        void sweepChildren(JSRuntime* rt);
        bool isMarkedFromAnyThread(JSRuntime* rt);
    };

    // Dummy entries are created for jitcode generated when profiling is not turned on,
    // so that they have representation in the global table if they are on the
    // stack when profiling is enabled.
    struct DummyEntry : public BaseEntry
    {
        void init(JitCode* code, void* nativeStartAddr, void* nativeEndAddr) {
            BaseEntry::init(Dummy, code, nativeStartAddr, nativeEndAddr);
        }

        void destroy() {}

        void* canonicalNativeAddrFor(JSRuntime* rt, void* ptr) const {
            return nullptr;
        }

        MOZ_MUST_USE bool callStackAtAddr(JSRuntime* rt, void* ptr, BytecodeLocationVector& results,
                                          uint32_t* depth) const
        {
            return true;
        }

        uint32_t callStackAtAddr(JSRuntime* rt, void* ptr, const char** results,
                                 uint32_t maxResults) const
        {
            return 0;
        }

        void youngestFrameLocationAtAddr(JSRuntime* rt, void* ptr,
                                         JSScript** script, jsbytecode** pc) const
        {
            *script = nullptr;
            *pc = nullptr;
        }
    };

    // QueryEntry is never stored in the table, just used for queries
    // where an instance of JitcodeGlobalEntry is required to do tree
    // lookups.
    struct QueryEntry : public BaseEntry
    {
        void init(void* addr) {
            BaseEntry::init(Query, nullptr, addr, addr);
        }
        uint8_t* addr() const {
            return reinterpret_cast<uint8_t*>(nativeStartAddr());
        }
        void destroy() {}
    };

  private:
    JitcodeSkiplistTower* tower_;

    union {
        // Shadowing BaseEntry instance to allow access to base fields
        // and type extraction.
        BaseEntry base_;

        // The most common entry type: describing jitcode generated by
        // Ion main-line code.
        IonEntry ion_;

        // Baseline jitcode.
        BaselineEntry baseline_;

        // IonCache stubs.
        IonCacheEntry ionCache_;

        // Dummy entries.
        DummyEntry dummy_;

        // When doing queries on the SplayTree for particular addresses,
        // the query addresses are representd using a QueryEntry.
        QueryEntry query_;
    };

  public:
    JitcodeGlobalEntry()
      : tower_(nullptr)
    {
        base_.init();
    }

    explicit JitcodeGlobalEntry(const IonEntry& ion)
      : tower_(nullptr)
    {
        ion_ = ion;
    }

    explicit JitcodeGlobalEntry(const BaselineEntry& baseline)
      : tower_(nullptr)
    {
        baseline_ = baseline;
    }

    explicit JitcodeGlobalEntry(const IonCacheEntry& ionCache)
      : tower_(nullptr)
    {
        ionCache_ = ionCache;
    }

    explicit JitcodeGlobalEntry(const DummyEntry& dummy)
      : tower_(nullptr)
    {
        dummy_ = dummy;
    }

    explicit JitcodeGlobalEntry(const QueryEntry& query)
      : tower_(nullptr)
    {
        query_ = query;
    }

    static JitcodeGlobalEntry MakeQuery(void* ptr) {
        QueryEntry query;
        query.init(ptr);
        return JitcodeGlobalEntry(query);
    }

    void destroy() {
        switch (kind()) {
          case Ion:
            ionEntry().destroy();
            break;
          case Baseline:
            baselineEntry().destroy();
            break;
          case IonCache:
            ionCacheEntry().destroy();
            break;
          case Dummy:
            dummyEntry().destroy();
            break;
          case Query:
            queryEntry().destroy();
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
    }

    JitCode* jitcode() const {
        return baseEntry().jitcode();
    }
    void* nativeStartAddr() const {
        return base_.nativeStartAddr();
    }
    void* nativeEndAddr() const {
        return base_.nativeEndAddr();
    }

    uint32_t generation() const {
        return baseEntry().generation();
    }
    void setGeneration(uint32_t gen) {
        baseEntry().setGeneration(gen);
    }
    void setAsExpired() {
        baseEntry().setGeneration(UINT32_MAX);
    }
    bool isSampled(uint32_t currentGen, uint32_t lapCount) {
        return baseEntry().isSampled(currentGen, lapCount);
    }

    bool startsBelowPointer(void* ptr) const {
        return base_.startsBelowPointer(ptr);
    }
    bool endsAbovePointer(void* ptr) const {
        return base_.endsAbovePointer(ptr);
    }
    bool containsPointer(void* ptr) const {
        return base_.containsPointer(ptr);
    }

    bool overlapsWith(const JitcodeGlobalEntry& entry) const {
        // Catch full containment of |entry| within |this|, and partial overlaps.
        if (containsPointer(entry.nativeStartAddr()) || containsPointer(entry.nativeEndAddr()))
            return true;

        // Catch full containment of |this| within |entry|.
        if (startsBelowPointer(entry.nativeEndAddr()) && endsAbovePointer(entry.nativeStartAddr()))
            return true;

        return false;
    }

    Kind kind() const {
        return base_.kind();
    }

    bool isValid() const {
        return (kind() > INVALID) && (kind() < LIMIT);
    }
    bool isIon() const {
        return kind() == Ion;
    }
    bool isBaseline() const {
        return kind() == Baseline;
    }
    bool isIonCache() const {
        return kind() == IonCache;
    }
    bool isDummy() const {
        return kind() == Dummy;
    }
    bool isQuery() const {
        return kind() == Query;
    }

    BaseEntry& baseEntry() {
        MOZ_ASSERT(isValid());
        return base_;
    }
    IonEntry& ionEntry() {
        MOZ_ASSERT(isIon());
        return ion_;
    }
    BaselineEntry& baselineEntry() {
        MOZ_ASSERT(isBaseline());
        return baseline_;
    }
    IonCacheEntry& ionCacheEntry() {
        MOZ_ASSERT(isIonCache());
        return ionCache_;
    }
    DummyEntry& dummyEntry() {
        MOZ_ASSERT(isDummy());
        return dummy_;
    }
    QueryEntry& queryEntry() {
        MOZ_ASSERT(isQuery());
        return query_;
    }

    const BaseEntry& baseEntry() const {
        MOZ_ASSERT(isValid());
        return base_;
    }
    const IonEntry& ionEntry() const {
        MOZ_ASSERT(isIon());
        return ion_;
    }
    const BaselineEntry& baselineEntry() const {
        MOZ_ASSERT(isBaseline());
        return baseline_;
    }
    const IonCacheEntry& ionCacheEntry() const {
        MOZ_ASSERT(isIonCache());
        return ionCache_;
    }
    const DummyEntry& dummyEntry() const {
        MOZ_ASSERT(isDummy());
        return dummy_;
    }
    const QueryEntry& queryEntry() const {
        MOZ_ASSERT(isQuery());
        return query_;
    }

    void* canonicalNativeAddrFor(JSRuntime* rt, void* ptr) const {
        switch (kind()) {
          case Ion:
            return ionEntry().canonicalNativeAddrFor(rt, ptr);
          case Baseline:
            return baselineEntry().canonicalNativeAddrFor(rt, ptr);
          case IonCache:
            return ionCacheEntry().canonicalNativeAddrFor(rt, ptr);
          case Dummy:
            return dummyEntry().canonicalNativeAddrFor(rt, ptr);
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
        return nullptr;
    }

    // Read the inline call stack at a given point in the native code and append into
    // the given vector.  Innermost (script,pc) pair will be appended first, and
    // outermost appended last.
    //
    // Returns false on memory failure.
    MOZ_MUST_USE bool callStackAtAddr(JSRuntime* rt, void* ptr, BytecodeLocationVector& results,
                                      uint32_t* depth) const
    {
        switch (kind()) {
          case Ion:
            return ionEntry().callStackAtAddr(rt, ptr, results, depth);
          case Baseline:
            return baselineEntry().callStackAtAddr(rt, ptr, results, depth);
          case IonCache:
            return ionCacheEntry().callStackAtAddr(rt, ptr, results, depth);
          case Dummy:
            return dummyEntry().callStackAtAddr(rt, ptr, results, depth);
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
        return false;
    }

    uint32_t callStackAtAddr(JSRuntime* rt, void* ptr, const char** results,
                             uint32_t maxResults) const
    {
        switch (kind()) {
          case Ion:
            return ionEntry().callStackAtAddr(rt, ptr, results, maxResults);
          case Baseline:
            return baselineEntry().callStackAtAddr(rt, ptr, results, maxResults);
          case IonCache:
            return ionCacheEntry().callStackAtAddr(rt, ptr, results, maxResults);
          case Dummy:
            return dummyEntry().callStackAtAddr(rt, ptr, results, maxResults);
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
        return false;
    }

    void youngestFrameLocationAtAddr(JSRuntime* rt, void* ptr,
                                     JSScript** script, jsbytecode** pc) const
    {
        switch (kind()) {
          case Ion:
            return ionEntry().youngestFrameLocationAtAddr(rt, ptr, script, pc);
          case Baseline:
            return baselineEntry().youngestFrameLocationAtAddr(rt, ptr, script, pc);
          case IonCache:
            return ionCacheEntry().youngestFrameLocationAtAddr(rt, ptr, script, pc);
          case Dummy:
            return dummyEntry().youngestFrameLocationAtAddr(rt, ptr, script, pc);
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
    }

    // Figure out the number of the (JSScript*, jsbytecode*) pairs that are active
    // at this location.
    uint32_t lookupInlineCallDepth(void* ptr);

    // Compare two global entries.
    static int compare(const JitcodeGlobalEntry& ent1, const JitcodeGlobalEntry& ent2);
    int compareTo(const JitcodeGlobalEntry& other) {
        return compare(*this, other);
    }

    // Compute a profiling string for a given script.
    static char* createScriptString(JSContext* cx, JSScript* script, size_t* length=nullptr);

    bool hasTrackedOptimizations() const {
        switch (kind()) {
          case Ion:
            return ionEntry().hasTrackedOptimizations();
          case IonCache:
            return ionCacheEntry().hasTrackedOptimizations();
          case Baseline:
          case Dummy:
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
        return false;
    }

    mozilla::Maybe<uint8_t> trackedOptimizationIndexAtAddr(
            JSRuntime *rt,
            void* addr,
            uint32_t* entryOffsetOut)
    {
        switch (kind()) {
          case Ion:
            return ionEntry().trackedOptimizationIndexAtAddr(rt, addr, entryOffsetOut);
          case IonCache:
            return ionCacheEntry().trackedOptimizationIndexAtAddr(rt, addr, entryOffsetOut);
          case Baseline:
          case Dummy:
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
        return mozilla::Nothing();
    }

    void forEachOptimizationAttempt(JSRuntime* rt, uint8_t index,
                                    JS::ForEachTrackedOptimizationAttemptOp& op)
    {
        switch (kind()) {
          case Ion:
            ionEntry().forEachOptimizationAttempt(rt, index, op);
            return;
          case IonCache:
            ionCacheEntry().forEachOptimizationAttempt(rt, index, op);
            return;
          case Baseline:
          case Dummy:
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
    }

    void forEachOptimizationTypeInfo(JSRuntime* rt, uint8_t index,
                                     IonTrackedOptimizationsTypeInfo::ForEachOpAdapter& op)
    {
        switch (kind()) {
          case Ion:
            ionEntry().forEachOptimizationTypeInfo(rt, index, op);
            return;
          case IonCache:
            ionCacheEntry().forEachOptimizationTypeInfo(rt, index, op);
            return;
          case Baseline:
          case Dummy:
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
    }

    IonTrackedOptimizationsAttempts trackedOptimizationAttempts(uint8_t index) {
        return ionEntry().trackedOptimizationAttempts(index);
    }

    IonTrackedOptimizationsTypeInfo trackedOptimizationTypeInfo(uint8_t index) {
        return ionEntry().trackedOptimizationTypeInfo(index);
    }

    const IonTrackedTypeVector* allTrackedTypes() {
        return ionEntry().allTrackedTypes();
    }

    Zone* zone() {
        return baseEntry().jitcode()->zone();
    }

    template <class ShouldMarkProvider>
    bool mark(JSTracer* trc) {
        bool markedAny = baseEntry().markJitcode<ShouldMarkProvider>(trc);
        switch (kind()) {
          case Ion:
            markedAny |= ionEntry().mark<ShouldMarkProvider>(trc);
            break;
          case Baseline:
            markedAny |= baselineEntry().mark<ShouldMarkProvider>(trc);
            break;
          case IonCache:
            markedAny |= ionCacheEntry().mark<ShouldMarkProvider>(trc);
            break;
          case Dummy:
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
        return markedAny;
    }

    void sweepChildren(JSRuntime* rt) {
        switch (kind()) {
          case Ion:
            ionEntry().sweepChildren();
            break;
          case Baseline:
            baselineEntry().sweepChildren();
            break;
          case IonCache:
            ionCacheEntry().sweepChildren(rt);
            break;
          case Dummy:
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
    }

    bool isMarkedFromAnyThread(JSRuntime* rt) {
        if (!baseEntry().isJitcodeMarkedFromAnyThread(rt))
            return false;
        switch (kind()) {
          case Ion:
            return ionEntry().isMarkedFromAnyThread(rt);
          case Baseline:
            return baselineEntry().isMarkedFromAnyThread(rt);
          case IonCache:
            return ionCacheEntry().isMarkedFromAnyThread(rt);
          case Dummy:
            break;
          default:
            MOZ_CRASH("Invalid JitcodeGlobalEntry kind.");
        }
        return true;
    }

    //
    // When stored in a free-list, entries use 'tower_' to store a
    // pointer to the next entry.  In this context only, 'tower_'
    // may refer to a |JitcodeGlobalEntry*| instead of a
    // |JitcodeSkiplistTower*|.
    //

    void addToFreeList(JitcodeGlobalEntry** freeList) {
        MOZ_ASSERT(!isValid());

        JitcodeGlobalEntry* nextFreeEntry = *freeList;
        MOZ_ASSERT_IF(nextFreeEntry, !nextFreeEntry->isValid());

        tower_ = (JitcodeSkiplistTower*) nextFreeEntry;
        *freeList = this;
    }

    static JitcodeGlobalEntry* PopFromFreeList(JitcodeGlobalEntry** freeList) {
        if (!*freeList)
            return nullptr;

        JitcodeGlobalEntry* entry = *freeList;
        MOZ_ASSERT(!entry->isValid());
        JitcodeGlobalEntry* nextFreeEntry = (JitcodeGlobalEntry*) entry->tower_;
        entry->tower_ = nullptr;
        *freeList = nextFreeEntry;
        return entry;
    }
};

/*
 * Global table of JitcodeGlobalEntry values sorted by native address range.
 */
class JitcodeGlobalTable
{
  private:
    static const size_t LIFO_CHUNK_SIZE = 16 * 1024;

    LifoAlloc alloc_;
    JitcodeGlobalEntry* freeEntries_;
    uint32_t rand_;
    uint32_t skiplistSize_;

    JitcodeGlobalEntry* startTower_[JitcodeSkiplistTower::MAX_HEIGHT];
    JitcodeSkiplistTower* freeTowers_[JitcodeSkiplistTower::MAX_HEIGHT];

  public:
    JitcodeGlobalTable()
      : alloc_(LIFO_CHUNK_SIZE), freeEntries_(nullptr), rand_(0), skiplistSize_(0)
    {
        for (unsigned i = 0; i < JitcodeSkiplistTower::MAX_HEIGHT; i++)
            startTower_[i] = nullptr;
        for (unsigned i = 0; i < JitcodeSkiplistTower::MAX_HEIGHT; i++)
            freeTowers_[i] = nullptr;
    }
    ~JitcodeGlobalTable() {}

    bool empty() const {
        return skiplistSize_ == 0;
    }

    const JitcodeGlobalEntry* lookup(void* ptr) {
        return lookupInternal(ptr);
    }

    JitcodeGlobalEntry& lookupInfallible(void* ptr) {
        JitcodeGlobalEntry* entry = lookupInternal(ptr);
        MOZ_ASSERT(entry);
        return *entry;
    }

    const JitcodeGlobalEntry& lookupForSamplerInfallible(void* ptr, JSRuntime* rt,
                                                         uint32_t sampleBufferGen);

    MOZ_MUST_USE bool addEntry(const JitcodeGlobalEntry::IonEntry& entry, JSRuntime* rt) {
        return addEntry(JitcodeGlobalEntry(entry), rt);
    }
    MOZ_MUST_USE bool addEntry(const JitcodeGlobalEntry::BaselineEntry& entry, JSRuntime* rt) {
        return addEntry(JitcodeGlobalEntry(entry), rt);
    }
    MOZ_MUST_USE bool addEntry(const JitcodeGlobalEntry::IonCacheEntry& entry, JSRuntime* rt) {
        return addEntry(JitcodeGlobalEntry(entry), rt);
    }
    MOZ_MUST_USE bool addEntry(const JitcodeGlobalEntry::DummyEntry& entry, JSRuntime* rt) {
        return addEntry(JitcodeGlobalEntry(entry), rt);
    }

    void removeEntry(JitcodeGlobalEntry& entry, JitcodeGlobalEntry** prevTower, JSRuntime* rt);
    void releaseEntry(JitcodeGlobalEntry& entry, JitcodeGlobalEntry** prevTower, JSRuntime* rt);

    void setAllEntriesAsExpired(JSRuntime* rt);
    void markUnconditionally(JSTracer* trc);
    MOZ_MUST_USE bool markIteratively(JSTracer* trc);
    void sweep(JSRuntime* rt);

  private:
    MOZ_MUST_USE bool addEntry(const JitcodeGlobalEntry& entry, JSRuntime* rt);

    JitcodeGlobalEntry* lookupInternal(void* ptr);

    // Initialize towerOut such that towerOut[i] (for i in [0, MAX_HEIGHT-1])
    // is a JitcodeGlobalEntry that is sorted to be <query, whose successor at
    // level i is either null, or sorted to be >= query.
    //
    // If entry with the given properties does not exist for level i, then
    // towerOut[i] is initialized to nullptr.
    void searchInternal(const JitcodeGlobalEntry& query, JitcodeGlobalEntry** towerOut);

    JitcodeGlobalEntry* searchAtHeight(unsigned level, JitcodeGlobalEntry* start,
                                       const JitcodeGlobalEntry& query);

    // Calculate next random tower height.
    unsigned generateTowerHeight();

    JitcodeSkiplistTower* allocateTower(unsigned height);
    JitcodeGlobalEntry* allocateEntry();

#ifdef DEBUG
    void verifySkiplist();
#else
    void verifySkiplist() {}
#endif

  public:
    class Range
    {
      protected:
        JitcodeGlobalTable& table_;
        JitcodeGlobalEntry* cur_;

      public:
        explicit Range(JitcodeGlobalTable& table)
          : table_(table),
            cur_(table.startTower_[0])
        { }

        JitcodeGlobalEntry* front() const {
            MOZ_ASSERT(!empty());
            return cur_;
        }

        bool empty() const {
            return !cur_;
        }

        void popFront() {
            MOZ_ASSERT(!empty());
            cur_ = cur_->tower_->next(0);
        }
    };

    // An enumerator class that can remove entries as it enumerates. If this
    // functionality is not needed, use Range instead.
    class Enum : public Range
    {
        JSRuntime* rt_;
        JitcodeGlobalEntry* next_;
        JitcodeGlobalEntry* prevTower_[JitcodeSkiplistTower::MAX_HEIGHT];

      public:
        Enum(JitcodeGlobalTable& table, JSRuntime* rt);

        void popFront();
        void removeFront();
    };
};


/*
 * Container class for main jitcode table.
 * The Region table's memory is structured as follows:
 *
 *      +------------------------------------------------+   |
 *      |  Region 1 Run                                  |   |
 *      |------------------------------------------------|   |
 *      |  Region 2 Run                                  |   |
 *      |                                                |   |
 *      |                                                |   |
 *      |------------------------------------------------|   |
 *      |  Region 3 Run                                  |   |
 *      |                                                |   |
 *      |------------------------------------------------|   |-- Payload
 *      |                                                |   |
 *      |               ...                              |   |
 *      |                                                |   |
 *      |------------------------------------------------|   |
 *      |  Region M Run                                  |   |
 *      |                                                |   |
 *      +================================================+ <- RegionTable pointer points here
 *      | uint23_t numRegions = M                        |   |
 *      +------------------------------------------------+   |
 *      | Region 1                                       |   |
 *      |   uint32_t entryOffset = size(Payload)         |   |
 *      +------------------------------------------------+   |
 *      |                                                |   |-- Table
 *      |   ...                                          |   |
 *      |                                                |   |
 *      +------------------------------------------------+   |
 *      | Region M                                       |   |
 *      |   uint32_t entryOffset                         |   |
 *      +------------------------------------------------+   |
 *
 * The region table is composed of two sections: a tail section that contains a table of
 * fixed-size entries containing offsets into the the head section, and a head section that
 * holds a sequence of variable-sized runs.  The table in the tail section serves to
 * locate the variable-length encoded structures in the head section.
 *
 * The entryOffsets in the table indicate the bytes offset to subtract from the regionTable
 * pointer to arrive at the encoded region in the payload.
 *
 *
 * Variable-length entries in payload
 * ----------------------------------
 * The entryOffsets in the region table's fixed-sized entries refer to a location within the
 * variable-length payload section.  This location contains a compactly encoded "run" of
 * mappings.
 *
 * Each run starts by describing the offset within the native code it starts at, and the
 * sequence of (JSScript*, jsbytecode*) pairs active at that site.  Following that, there
 * are a number of variable-length entries encoding (nativeOffsetDelta, bytecodeOffsetDelta)
 * pairs for the run.
 *
 *      VarUint32 nativeOffset;
 *          - The offset from nativeStartAddr in the global table entry at which
 *            the jitcode for this region starts.
 *
 *      Uint8_t scriptDepth;
 *          - The depth of inlined scripts for this region.
 *
 *      List<VarUint32> inlineScriptPcStack;
 *          - We encode (2 * scriptDepth) VarUint32s here.  Each pair of uint32s are taken
 *            as an index into the scriptList in the global table entry, and a pcOffset
 *            respectively.
 *
 *      List<NativeAndBytecodeDelta> deltaRun;
 *          - The rest of the entry is a deltaRun that stores a series of variable-length
 *            encoded NativeAndBytecodeDelta datums.
 */
class JitcodeRegionEntry
{
  private:
    static const unsigned MAX_RUN_LENGTH = 100;

  public:
    static void WriteHead(CompactBufferWriter& writer,
                          uint32_t nativeOffset, uint8_t scriptDepth);
    static void ReadHead(CompactBufferReader& reader,
                         uint32_t* nativeOffset, uint8_t* scriptDepth);

    static void WriteScriptPc(CompactBufferWriter& writer, uint32_t scriptIdx, uint32_t pcOffset);
    static void ReadScriptPc(CompactBufferReader& reader, uint32_t* scriptIdx, uint32_t* pcOffset);

    static void WriteDelta(CompactBufferWriter& writer, uint32_t nativeDelta, int32_t pcDelta);
    static void ReadDelta(CompactBufferReader& reader, uint32_t* nativeDelta, int32_t* pcDelta);

    // Given a pointer into an array of NativeToBytecode (and a pointer to the end of the array),
    // compute the number of entries that would be consume by outputting a run starting
    // at this one.
    static uint32_t ExpectedRunLength(const CodeGeneratorShared::NativeToBytecode* entry,
                                      const CodeGeneratorShared::NativeToBytecode* end);

    // Write a run, starting at the given NativeToBytecode entry, into the given buffer writer.
    static MOZ_MUST_USE bool WriteRun(CompactBufferWriter& writer, JSScript** scriptList,
                                      uint32_t scriptListSize, uint32_t runLength,
                                      const CodeGeneratorShared::NativeToBytecode* entry);

    // Delta Run entry formats are encoded little-endian:
    //
    //  byte 0
    //  NNNN-BBB0
    //      Single byte format.  nativeDelta in [0, 15], pcDelta in [0, 7]
    //
    static const uint32_t ENC1_MASK = 0x1;
    static const uint32_t ENC1_MASK_VAL = 0x0;

    static const uint32_t ENC1_NATIVE_DELTA_MAX = 0xf;
    static const unsigned ENC1_NATIVE_DELTA_SHIFT = 4;

    static const uint32_t ENC1_PC_DELTA_MASK = 0x0e;
    static const int32_t ENC1_PC_DELTA_MAX = 0x7;
    static const unsigned ENC1_PC_DELTA_SHIFT = 1;

    //  byte 1    byte 0
    //  NNNN-NNNN BBBB-BB01
    //      Two-byte format.  nativeDelta in [0, 255], pcDelta in [0, 63]
    //
    static const uint32_t ENC2_MASK = 0x3;
    static const uint32_t ENC2_MASK_VAL = 0x1;

    static const uint32_t ENC2_NATIVE_DELTA_MAX = 0xff;
    static const unsigned ENC2_NATIVE_DELTA_SHIFT = 8;

    static const uint32_t ENC2_PC_DELTA_MASK = 0x00fc;
    static const int32_t ENC2_PC_DELTA_MAX = 0x3f;
    static const unsigned ENC2_PC_DELTA_SHIFT = 2;

    //  byte 2    byte 1    byte 0
    //  NNNN-NNNN NNNB-BBBB BBBB-B011
    //      Three-byte format.  nativeDelta in [0, 2047], pcDelta in [-512, 511]
    //
    static const uint32_t ENC3_MASK = 0x7;
    static const uint32_t ENC3_MASK_VAL = 0x3;

    static const uint32_t ENC3_NATIVE_DELTA_MAX = 0x7ff;
    static const unsigned ENC3_NATIVE_DELTA_SHIFT = 13;

    static const uint32_t ENC3_PC_DELTA_MASK = 0x001ff8;
    static const int32_t ENC3_PC_DELTA_MAX = 0x1ff;
    static const int32_t ENC3_PC_DELTA_MIN = -ENC3_PC_DELTA_MAX - 1;
    static const unsigned ENC3_PC_DELTA_SHIFT = 3;

    //  byte 3    byte 2    byte 1    byte 0
    //  NNNN-NNNN NNNN-NNNN BBBB-BBBB BBBB-B111
    //      Three-byte format.  nativeDelta in [0, 65535], pcDelta in [-4096, 4095]
    static const uint32_t ENC4_MASK = 0x7;
    static const uint32_t ENC4_MASK_VAL = 0x7;

    static const uint32_t ENC4_NATIVE_DELTA_MAX = 0xffff;
    static const unsigned ENC4_NATIVE_DELTA_SHIFT = 16;

    static const uint32_t ENC4_PC_DELTA_MASK = 0x0000fff8;
    static const int32_t ENC4_PC_DELTA_MAX = 0xfff;
    static const int32_t ENC4_PC_DELTA_MIN = -ENC4_PC_DELTA_MAX - 1;
    static const unsigned ENC4_PC_DELTA_SHIFT = 3;

    static bool IsDeltaEncodeable(uint32_t nativeDelta, int32_t pcDelta) {
        return (nativeDelta <= ENC4_NATIVE_DELTA_MAX) &&
               (pcDelta >= ENC4_PC_DELTA_MIN) && (pcDelta <= ENC4_PC_DELTA_MAX);
    }

  private:
    const uint8_t* data_;
    const uint8_t* end_;

    // Unpacked state from jitcode entry.
    uint32_t nativeOffset_;
    uint8_t scriptDepth_;
    const uint8_t* scriptPcStack_;
    const uint8_t* deltaRun_;

    void unpack();

  public:
    JitcodeRegionEntry(const uint8_t* data, const uint8_t* end)
      : data_(data), end_(end),
        nativeOffset_(0), scriptDepth_(0),
        scriptPcStack_(nullptr), deltaRun_(nullptr)
    {
        MOZ_ASSERT(data_ < end_);
        unpack();
        MOZ_ASSERT(scriptPcStack_ < end_);
        MOZ_ASSERT(deltaRun_ <= end_);
    }

    uint32_t nativeOffset() const {
        return nativeOffset_;
    }
    uint32_t scriptDepth() const {
        return scriptDepth_;
    }

    class ScriptPcIterator
    {
      private:
        uint32_t count_;
        const uint8_t* start_;
        const uint8_t* end_;

        uint32_t idx_;
        const uint8_t* cur_;

      public:
        ScriptPcIterator(uint32_t count, const uint8_t* start, const uint8_t* end)
          : count_(count), start_(start), end_(end), idx_(0), cur_(start_)
        {}

        bool hasMore() const
        {
            MOZ_ASSERT((idx_ == count_) == (cur_ == end_));
            MOZ_ASSERT((idx_ < count_) == (cur_ < end_));
            return cur_ < end_;
        }

        void readNext(uint32_t* scriptIdxOut, uint32_t* pcOffsetOut)
        {
            MOZ_ASSERT(scriptIdxOut);
            MOZ_ASSERT(pcOffsetOut);
            MOZ_ASSERT(hasMore());

            CompactBufferReader reader(cur_, end_);
            ReadScriptPc(reader, scriptIdxOut, pcOffsetOut);

            cur_ = reader.currentPosition();
            MOZ_ASSERT(cur_ <= end_);

            idx_++;
            MOZ_ASSERT_IF(idx_ == count_, cur_ == end_);
        }

        void reset() {
            idx_ = 0;
            cur_ = start_;
        }
    };

    ScriptPcIterator scriptPcIterator() const {
        // End of script+pc sequence is the start of the delta run.
        return ScriptPcIterator(scriptDepth_, scriptPcStack_,  deltaRun_);
    }

    class DeltaIterator {
      private:
        const uint8_t* start_;
        const uint8_t* end_;
        const uint8_t* cur_;

      public:
        DeltaIterator(const uint8_t* start, const uint8_t* end)
          : start_(start), end_(end), cur_(start)
        {}

        bool hasMore() const
        {
            MOZ_ASSERT(cur_ <= end_);
            return cur_ < end_;
        }

        void readNext(uint32_t* nativeDeltaOut, int32_t* pcDeltaOut)
        {
            MOZ_ASSERT(nativeDeltaOut != nullptr);
            MOZ_ASSERT(pcDeltaOut != nullptr);

            MOZ_ASSERT(hasMore());

            CompactBufferReader reader(cur_, end_);
            ReadDelta(reader, nativeDeltaOut, pcDeltaOut);

            cur_ = reader.currentPosition();
            MOZ_ASSERT(cur_ <= end_);
        }

        void reset() {
            cur_ = start_;
        }
    };
    DeltaIterator deltaIterator() const {
        return DeltaIterator(deltaRun_, end_);
    }

    uint32_t findPcOffset(uint32_t queryNativeOffset, uint32_t startPcOffset) const;
};

class JitcodeIonTable
{
  private:
    /* Variable length payload section "below" here. */
    uint32_t numRegions_;
    uint32_t regionOffsets_[1];

    const uint8_t* payloadEnd() const {
        return reinterpret_cast<const uint8_t*>(this);
    }

  public:
    explicit JitcodeIonTable(uint32_t numRegions)
      : numRegions_(numRegions)
    {
        for (uint32_t i = 0; i < numRegions; i++)
            regionOffsets_[i] = 0;
    }

    MOZ_MUST_USE bool makeIonEntry(JSContext* cx, JitCode* code, uint32_t numScripts,
                                   JSScript** scripts, JitcodeGlobalEntry::IonEntry& out);

    uint32_t numRegions() const {
        return numRegions_;
    }

    uint32_t regionOffset(uint32_t regionIndex) const {
        MOZ_ASSERT(regionIndex < numRegions());
        return regionOffsets_[regionIndex];
    }

    JitcodeRegionEntry regionEntry(uint32_t regionIndex) const {
        const uint8_t* regionStart = payloadEnd() - regionOffset(regionIndex);
        const uint8_t* regionEnd = payloadEnd();
        if (regionIndex < numRegions_ - 1)
            regionEnd -= regionOffset(regionIndex + 1);
        return JitcodeRegionEntry(regionStart, regionEnd);
    }

    bool regionContainsOffset(uint32_t regionIndex, uint32_t nativeOffset) {
        MOZ_ASSERT(regionIndex < numRegions());

        JitcodeRegionEntry ent = regionEntry(regionIndex);
        if (nativeOffset < ent.nativeOffset())
            return false;

        if (regionIndex == numRegions_ - 1)
            return true;

        return nativeOffset < regionEntry(regionIndex + 1).nativeOffset();
    }

    uint32_t findRegionEntry(uint32_t offset) const;

    const uint8_t* payloadStart() const {
        // The beginning of the payload the beginning of the first region are the same.
        return payloadEnd() - regionOffset(0);
    }

    static MOZ_MUST_USE bool WriteIonTable(CompactBufferWriter& writer,
                                           JSScript** scriptList, uint32_t scriptListSize,
                                           const CodeGeneratorShared::NativeToBytecode* start,
                                           const CodeGeneratorShared::NativeToBytecode* end,
                                           uint32_t* tableOffsetOut, uint32_t* numRegionsOut);
};


} // namespace jit
} // namespace js

#endif /* jit_JitcodeMap_h */
